Improving carotenoid production in recombinant yeast, Saccharomyces cerevisiae, using ultrasound-irradiated two-phase extractive fermentation.

Carotenoids are hydrophobic compounds that exhibit excellent bioactivity and can be produced by recombinant S. cerevisiae. Irradiating microorganisms with ultrasonic waves increase the productivity of various useful chemicals. Ultrasonic waves are also used to extract useful chemicals that accumulate in microbial cells. In this study, we aimed to improve the carotenoid production efficiency of a recombinant S. cerevisiae using an ultrasonic-irradiation based two-phase extractive fermentation process. When isopropyl myristate was used as the extraction solvent, a total of 264 mg/L of carotenoid was produced when batches were subjected to ultrasonic-irradiation at 10 W, which was a 1.3-fold increase when compared to the control. Transcriptome analysis suggested that one of the reasons for this improvement was an increase in the number of living cells. In fact, after 96 h of fermentation, the number of living cells increased by 1.4-fold upon irradiation with ultrasonic waves. Consequently, we succeeded in improving the carotenoid production in a recombinant S. cerevisiae strain using a ultrasonic-irradiated two-phase extractive fermentation and isopropyl myristate as the solvent. This fermentation strategy has the potential to be widely applied during the production of hydrophobic chemicals in recombinant yeast, and future research is expected to further develop this process.

Modulation of gene expression by cocktail δ-integration to improve carotenoid production in Saccharomyces cerevisiae.

Carotenoids, including ß-carotene, are commercially valuable compounds, and their production by engineered Saccharomyces cerevisiae is a promising strategy for their industrial production. Here, to improve ß-carotene productivity in engineered S. cerevisiae, a cocktail δ-integration strategy, which involves simultaneous integration of various multi-copy genes, followed by selection of desirable transformants, was applied for modulation of ß-carotene production-related genes expression. The engineered strain, YPH499/Mo3Crt79, was constructed by three repeated rounds of cocktail δ-integration using CrtE, CrtYB, and CrtI derived from the yeast, Xanthophyllomyces dendrorhous. The recombinant strain produced 7.3 mg/L of carotenoids in 48 h and 52.3 mg/L of ß-carotene in 96 h, which were greater values than those achieved by CrtE, CrtYB, and CrtI co-overexpressing strains. Therefore, repeated cocktail δ-integration was effective in improving carotenoid productivity in S. cerevisiae and could be a promising technique for constructing metabolically engineered S. cerevisiae capable of producing bio-based chemicals.